The move was first reported by the Baltimore Sun.
Smith, 31, comes to Baltimore on a one-year deal after spending his first nine seasons with Jacksonville, which selected him in the second round of the 2004 draft. He has been a consistent performer throughout his career and is the Jaguars' all-time leader with 1,090 tackles.
But Smith was available this long because he's a bit of a question mark going forward. He was limited to just two games in 2012 because of a groin injury and will be looking to regain his previous form.
But the Ravens are bringing in a player who had missed no more than two games in any of his first eight NFL seasons. He started all but three of Jacksonville's games from 2005-11, recording at least 100 tackles in each of those years.
Smith has made 21.5 career sacks, forced nine fumbles and picked off six passes in his career. In 2011, his last full healthy season, he made 107 tackles, defended eight passes and forced two fumbles.
If at full speed, Smith should help the Ravens overcome the losses of Ray Lewis and Dannell Ellerbe, while allowing Jameel McClain to ease his way back to work after missing the end of last season with a spinal cord contusion.
Rolando McClain was originally signed for inside depth, but he has since retired to deal with his personal life following his third arrest since 2011.
The team waived linebacker Michael McAdoo to make room on the roster.